Evolution of a radio access method and a radio network of a cellular mobile communication (hereinafter referred to as “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) is being examined in the 3rd Generation Partnership Project (3GPP). In the LTE, as a communication system for radio communication (downlink) from a base station apparatus to a mobile station apparatus, the Orthogonal Frequency Division Multiplexing (OFDM) system which is a multiple-carrier transmission is used. In addition, as a communication system of the radio communication (uplink) from the mobile station apparatus to the base station apparatus, the Single-Carrier Frequency Division Multiple Access (SC-FDMA) system which is a single-carrier transmission is used.
In the LTE, the base station apparatus instructs the mobile station apparatus to perform initial transmission or retransmission of PUSCH (Physical Uplink Shared Channel) which is a channel for uplink data (or referred to as “uplink shared channel: UL-SCH”) transmission by using Downlink Control Information (DCI) transmitted via PDCCH (Physical Downlink Control Channel). In the LTE, the mobile station apparatus transmits PUSCH by using one transmission antenna port.
In the LTE-A, use of SU (single user)-MIMO (Multiple Input Multiple Output) for the PUSCH is being examined in order to improve spectrum efficiency of the uplink. By using the SU-MIMO, the mobile station apparatus can spatially multiplex a plurality of pieces of uplink data in one PUSCH and transmit it by using a plurality of antenna ports. In the LTE, MU (multi user)-MIMO is used which is a technology to improve the spectrum efficiency in which a plurality of the mobile station apparatuses transmits data at the same time and the same frequency and the base station apparatus, when receiving the data, separates data of one or more sequences transmitted by each of the mobile station apparatuses, but in the LTE-A, expansion of the functions of MU-MIMO is being examined.
In the LTE, a cyclic shift has been introduced to a reference signal (Demodulation Reference Signal: DMRS) used for channel estimation and transmitted together with the PUSCH in order to reduce interference. Non-Patent Document 1 describes introduction of OCC (Orthogonal Cover Code) into the DMRS in order to further reduce interference of the DMRS during SU-MIMO and MU-MIMO. Moreover, Non-Patent Document 1 describes that information relating to the cyclic shift used for the DMRS and included in the downlink control information for the PUSCH is associated with the OCC used for the DMRS.